Globalization and international trade have impacted organisms around the world leading to a considerable number of species establishing in new geographic areas. Many organisms have taken advantage of human-made environments, including buildings. One such species is the dry rot fungus Serpula lacrymans, which is the most aggressive wood-decay fungus in indoor environments in temperate regions. Using population genomic analyses of 36 full genome sequenced isolates, we demonstrated that European and Japanese isolates are highly divergent and the populations split 3000-19,000 generations ago, probably predating human influence. Approximately 250 generations ago, the European population went through a tight bottleneck, probably corresponding to the fungus colonization of the built environment in Europe. The demographic history of these populations, probably lead to low adaptive potential. Only two loci under selection were identified using a Fst outlier approach, and selective sweep analyses identified three loci with extended haplotype homozygosity. The selective sweep analyses found signals in genes possibly related to decay of various substrates in Japan and in genes involved DNA replication and protein modification in Europe. Our results suggest that the dry rot fungus independently established in indoor environments in Europe and Japan and that invasive species can potentially establish large populations in new habitats based on a few colonizing individuals.
Ecological niche breadth and the mechanisms facilitating its evolution are fundamental to understanding adaptation to changing environments, persistence of generalist and specialist lineages and the formation of new species. Woody substrates are structurally complex resources utilized by organisms with specialized decay machinery. Wood-decaying fungi represent ideal model systems to study evolution of niche breadth, as they vary greatly in their host range and preferred decay stage of the substrate. In order to dissect the genetic basis for niche specialization in the invasive brown rot fungus Serpula lacrymans , we used phenotyping and integrative analysis of phylogenomic and transcriptomic data to compare this species to wild relatives in the Serpulaceae with a range of specialist to generalist decay strategies. Our results indicate specialist species have rewired regulatory networks active during wood decay towards decreased reliance on enzymatic machinery, and therefore nitrogen-intensive decay components. This shift was likely accompanied with adaptation to a narrow tree line habitat and switch to a pioneer decomposer strategy, both requiring rapid colonization of a nitrogen-limited substrate. Among substrate specialists with narrow niches, we also found evidence for pathways facilitating reversal to generalism, highlighting how evolution may move along different axes of niche space.
The coconut palm, an important cash and subsistence crop, is widely grown in the coastal regions of the tropics, including Mozambique. However, outbreak of an invasive and emerging coconut lethal yellowing disease (CLYD) is now a major challenge for the coconut industry and livelihood of millions of Mozambican. The observed successions of CLYD epidemics in Mozambique, suggest that other factors than plant-insect-phytoplasma triangle might be associated with the current disease trends. This study investigated the impact of Oryctes monoceros beetle on the CLYD epidemic in Mozambique, using questionnaire survey and direct observation in the fields. The results revealed that there was a significant and negative correlation between beetle and CLYD incidence. This negative correlation may be explained by beetle movement from adult CLYD-infected palms to younger palms which pose a great challenge to the replacement of palms lost due to CLYD. Management strategies must therefore stress the role of beetle larvae in palm trunks killed by CLYD and the threat of Oryces beetles to the replacement of death palm with new plantation.
Knowledge of putative insect species vectors of the coconut lethal yellowing disease (CLYD) in Mozambique is crucial to develop an effective disease management plan. Hemiptera specimens from the families Derbidae and Pentatomidae were collected in the Inhambane and Zambezia provinces of the coastal region of Mozambique in 2014, covering the two main growing seasons. Sequence analyses of the 16S rRNA gene were used for phytoplasma clustering. Polymerase chain reaction (PCR) amplification was performed employing three different primer sets specific for phytoplasma. BLAST sequence comparison and phylogenetic analysis of the 16S rDNA PCR products revealed that collected specimens of Derbidae Diostrombus mkurangai Wilson were carrying the CLYD phytoplasma. Virtual RFLP analyses of the obtained sequences confirmed this assigning the detected phytoplasmas to the 16SrXX-A subgroup, confirming that they are 'Candidatus Phytoplasma palmicola'-related strains. This is the first detection of a 'Candidatus Phytoplasma palmicola'-related strain in D. mkurangai.
ABSTRACT RNA stable isotope probing and high-throughput sequencing were used to characterize the active microbiomes of bacteria and fungi colonizing the roots and rhizosphere soil of oilseed rape to identify taxa assimilating plant-derived carbon following 13CO2 labeling. Root- and rhizosphere soil-associated communities of both bacteria and fungi differed from each other, and there were highly significant differences between their DNA- and RNA-based community profiles. Verrucomicrobia, Proteobacteria, Planctomycetes, Acidobacteria, Gemmatimonadetes, Actinobacteria, and Chloroflexi were the most active bacterial phyla in the rhizosphere soil. Bacteroidetes were more active in roots. The most abundant bacterial genera were well represented in both the 13C- and 12C-RNA fractions, while the fungal taxa were more differentiated. Streptomyces, Rhizobium, and Flavobacterium were dominant in roots, whereas Rhodoplanes and Sphingomonas (Kaistobacter) were dominant in rhizosphere soil. “Candidatus Nitrososphaera” was enriched in 13C in rhizosphere soil. Olpidium and Dendryphion were abundant in the 12C-RNA fraction of roots; Clonostachys was abundant in both roots and rhizosphere soil and heavily 13C enriched. Cryptococcus was dominant in rhizosphere soil and less abundant, but was 13C enriched in roots. The patterns of colonization and C acquisition revealed in this study assist in identifying microbial taxa that may be superior competitors for plant-derived carbon in the rhizosphere of Brassica napus. IMPORTANCE This microbiome study characterizes the active bacteria and fungi colonizing the roots and rhizosphere soil of Brassica napus using high-throughput sequencing and RNA-stable isotope probing. It identifies taxa assimilating plant-derived carbon following 13CO2 labeling and compares these with other less active groups not incorporating a plant assimilate. Brassica napus is an economically and globally important oilseed crop, cultivated for edible oil, biofuel production, and phytoextraction of heavy metals; however, it is susceptible to several diseases. The identification of the fungal and bacterial species successfully competing for plant-derived carbon, enabling them to colonize the roots and rhizosphere soil of this plant, should enable the identification of microorganisms that can be evaluated in more detailed functional studies and ultimately be used to improve plant health and productivity in sustainable agriculture.
Basidiomycete brown-rot fungi have a huge importance for wood decomposition and thus the global carbon cycle. Here, we present the genome sequence of Fomitopsis pinicola GR9-4 which represent different F. pinicola clade than the previously sequenced North American isolate FP-58527 SS1. The genome was sequenced by using a paired-end sequence library of Illumina and a 2.5k and 5k mate-pair library (ABI SOLiD). The final assembly adds up to a size of 45 Mb (including gaps between contigs), with a GC-content of 56%. The gene prediction resulted in 13,888 gene models. The genome sequence will be used as a basis for understanding population genomics, genome-wide association studies and wood decay mechanisms of this brown-rot fungus.
Nitrogen availability is often one of the limiting factors for intensive rice (Oryza sativa) cultivation. Rotation of rice with upland crops partially reduces nutrient depletion. This study was carried out at CaiLay district, Tien Giang province with the aim to investigate the effect of alternating the rice crop with maize (Zea mays) and mungbean (Phaseolus aureus)in different rotational systems on the diazotrophic community in soilusing pyrosequencing of the nifH genes. The results showed that the community structure of the diazotroph communities in soils were different when rice crop was alternated with either maize or mungbean crop than that in rice monoculture. The nifH sequences were highly diverse and assigned to eleven bacterial phyla and one Archaeal phylum. Proteobacteria and Firmicutes were the most common phyla carrying the nifH gene. The propotion of the Archaea, Betaproteobacteria, Cyanobacteria, Deltaproteobacteria, Firmicutes, Gammaproteobacteria and Nitrospira was significantly different among the treatments. The relative abundances of Anaeromyxobacter, and Geobacter were greater in RRR than in the RMgR treatment while Heliobacterium and Desulfosporosinus were higher in the RMgR than those in the RRR and RMR treatment.
To elucidate the genetic bases of mycorrhizal lifestyle evolution, we sequenced new fungal genomes, including 13 ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species, and five saprotrophs, which we analyzed along with other fungal genomes. Ectomycorrhizal fungi have a reduced complement of genes encoding plant cell wall-degrading enzymes (PCWDEs), as compared to their ancestral wood decayers. Nevertheless, they have retained a unique array of PCWDEs, thus suggesting that they possess diverse abilities to decompose lignocellulose. Similar functional categories of nonorthologous genes are induced in symbiosis. Of induced genes, 7-38% are orphan genes, including genes that encode secreted effector-like proteins. Convergent evolution of the mycorrhizal habit in fungi occurred via the repeated evolution of a 'symbiosis toolkit', with reduced numbers of PCWDEs and lineage-specific suites of mycorrhiza-induced genes.
Comparison of Biological Process annotations of R. solani genes between the induced (log2FPKM > 0) and repressed (log2FPKM
Over-represented Cellular Location terms from Gene Ontology (GO) of R. solani genes up- (a.) and down- (b.) regulated when confronted with S4 Serratia proteamaculans.
In this study, phytoplasmas associated with coconut lethal yellowing disease in Mozambique were characterized. For phylogenetic analysis the 16S rRNA genes were sequenced. Apart from ‘Candidatus Phytoplasma palmicola’ 16SrXXII-A, phylogenetic analysis revealed the presence of a double infection of ‘Ca. P. palmicola’ and a ‘Ca. P. pini’-related phytoplasmas. The second strain potentially represents a novel ‘Candidatus species’ and is closely related to ‘Ca. P. pini’.
Background Improved understanding of bacterial-fungal interactions in the rhizosphere should assist in the successful application of bacteria as biological control agents against fungal pathogens of plants, providing alternatives to chemicals in sustainable agriculture. Rhizoctonia solani is an important soil-associated fungal pathogen and its chemical treatment is not feasible or economic. The genomes of the plant-associated bacteria Serratia proteamaculans S4 and Serratia plymuthica AS13 have been sequenced, revealing genetic traits that may explain their diverse plant growth promoting activities and antagonistic interactions with R. solani . To understand the functional response of this pathogen to different bacteria and to elucidate whether the molecular mechanisms that the fungus exploits involve general stress or more specific responses, we performed a global transcriptome profiling of R. solani Rhs1AP anastomosis group 3 (AG-3) during interaction with the S4 and AS13 species of Serratia using RNA-seq. Results Approximately 104,504 million clean 75-100 bp paired-end reads were obtained from three libraries, each in triplicate (AG3-Control, AG3-S4 and AG3-AS13). Transcriptome analysis revealed that approximately 10 % of the fungal transcriptome was differentially expressed during challenge with Serratia . The numbers of S4- and AS13-specific differentially expressed genes (DEG) were 866 and 292 respectively, while there were 1035 common DEGs in the two treatment groups. Four hundred and sixty and 242 genes respectively had values of log 2 fold-change > 3 and for further analyses this cut-off value was used. Functional classification of DEGs based on Gene Ontology enrichment analysis and on KEGG pathway annotations revealed a general shift in fungal gene expression in which genes related to xenobiotic degradation, toxin and antioxidant production, energy, carbohydrate and lipid metabolism and hyphal rearrangements were subjected to transcriptional regulation. Conclusions This RNA-seq profiling generated a novel dataset describing the functional response of the phytopathogen R. solani AG3 to the plant-associated Serratia bacteria S4 and AS13. Most genes were regulated in the same way in the presence of both bacterial isolates, but there were also some strain-specific responses. The findings in this study will be beneficial for further research on biological control and in depth exploration of bacterial-fungal interactions in the rhizosphere.
SummaryRhizobacteria with biocontrol ability exploit a range of mechanisms to compete successfully with other microorganisms and to ensure their growth and survival in the rhizosphere, ultimately promoting plant growth. The rhizobacterium Serratia plymuthica AS13 is able to promote oilseed rape growth and improve seedling survival in the presence of the fungal pathogen, Rhizoctonia solani AG 2‐1; however, our understanding of the mechanisms underlying the antagonism of Serratia is limited. To elucidate possible mechanisms, genome‐wide gene expression profiling of S. plymuthica AS13 was carried out in the presence or absence of R. solani. We used RNA sequencing methodology to obtain a comprehensive overview of Serratia gene expression in response to R. solani. The differential gene expression profiles of S. plymuthica AS13 revealed significantly increased expression of genes related to the biosynthesis of the antibiotic pyrrolnitrin (prnABCD), protease production and transporters. The results presented here provide evidence that antibiosis is a major functional mechanism underlying the antagonistic behaviour of S. plymuthica AS13.
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In this study we investigated the genotypic diversity and the migration patterns of Phytophthora infestans in the Nordic countries. Isolates of P. infestans from outbreaks in 43 fields sampled in 2008 were collected using stratified sampling with country, field, and disease foci as the different strata. Microsatellites were used as markers to determine the genotypic variation in the sampled material. The results show a high genotypic variation of P. infestans in the Nordic countries with most of the genotypes found only once among the collected isolates. The major part of the genotypic variation was observed within the fields, with low differentiation between the fields. The observed low association of alleles among loci is consistent with frequent sexual reproduction of P. infestans in the Nordic countries. Coalescence analyses did not support a single common population for the four countries, thus indicating some degree of geographic differentiation. The analyses of migration patterns showed differing levels of gene flow among the Nordic countries. No correlation between migration rates and geographical distance could be seen. This could be explained by different degrees of genetic similarity between the pathogen populations in the different countries.
Serratia proteamaculans S4 (previously Serratia sp. S4), isolated from the rhizosphere of wild Equisetum sp., has the ability to stimulate plant growth and to suppress the growth of several soil-borne fungal pathogens of economically important crops. Here we present the non-contiguous, finished genome sequence of S. proteamaculans S4, which consists of a 5,324,944 bp circular chromosome and a 129,797 bp circular plasmid. The chromosome contains 5,008 predicted genes while the plasmid comprises 134 predicted genes. In total, 4,993 genes are assigned as protein-coding genes. The genome consists of 22 rRNA genes, 82 tRNA genes and 58 pseudogenes. This genome is a part of the project "Genomics of four rapeseed plant growth-promoting bacteria with antagonistic effect on plant pathogens" awarded through the 2010 DOE-JGI's Community Sequencing Program.
Problems with patchiness due to delay in emergence or poor crop establishment are not uncommon in oilseed rape cultivation. Our aim was to study the fungal communities associated with field grown oilseed rape and to explore their role in emergence and early crop establishment. This study was carried out by characterising the fungal communities in roots and rhizosphere soils of both spring and winter oilseed rape. The fungal communities were analysed using both culture-dependent and culture-independent approaches. Sampling was carried out in field plots with clear differences in crop establishment. Phylogenetic comparison of the fungal communities in different environments revealed significant differences between roots and rhizosphere soils. In winter rape, the fungal communities in the poor-emergence plots differed significantly from that found in normal-emergence plots, while in spring rape this difference was less prominent. However, in a combined statistical analysis of data from both winter and spring rape, the fungal communities in poor- and normal-emergence plots differed significantly. In follow-up studies, putatively pathogenic fungi were isolated from poor-emergence plots. Their effects on emergence and seedling growth were evaluated in the two crop types in greenhouse experiments. Rhizoctonia solani was found only in roots from poor-emergence plots, and was also demonstrated to be highly pathogenic on oilseed rape independent of cultivars when tested in greenhouse trials. The results from the fungal community analysis and from the greenhouse experiments are discussed in relation to their role in crop establishment related problems in oilseed rape.
Parasitism and saprotrophic wood decay are two fungal strategies fundamental for succession and nutrient cycling in forest ecosystems. An opportunity to assess the trade-off between these strategies is provided by the forest pathogen and wood decayer Heterobasidion annosum sensu lato. We report the annotated genome sequence and transcript profiling, as well as the quantitative trait loci mapping, of one member of the species complex: H. irregulare. Quantitative trait loci critical for pathogenicity, and rich in transposable elements, orphan and secreted genes, were identified. A wide range of cellulose-degrading enzymes are expressed during wood decay. By contrast, pathogenic interaction between H. irregulare and pine engages fewer carbohydrate-active enzymes, but involves an increase in pectinolytic enzymes, transcription modules for oxidative stress and secondary metabolite production. Our results show a trade-off in terms of constrained carbohydrate decomposition and membrane transport capacity during interaction with living hosts. Our findings establish that saprotrophic wood decay and necrotrophic parasitism involve two distinct, yet overlapping, processes.
Serratia plymuthica are plant-associated, plant beneficial species belonging to the family Enterobacteriaceae. The members of the genus Serratia are ubiquitous in nature and their life style varies from endophytic to free-living. S. plymuthica AS9 is of special interest for its ability to inhibit fungal pathogens of rapeseed and to promote plant growth. The genome of S. plymuthica AS9 comprises a 5,442,880 bp long circular chromosome that consists of 4,952 protein-coding genes, 87 tRNA genes and 7 rRNA operons. This genome is part of the project entitled "Genomics of four rapeseed plant growth promoting bacteria with antagonistic effect on plant pathogens" awarded through the 2010 DOE-JGI Community Sequencing Program (CSP2010).
Recent research on the evolution, phylogeography and population genetics of the dry rot fungus Serpula lacrymans is reviewed. The fungus causes severe damage to construction wood in temperate regions worldwide. Multi-locus genetic analyses have shown that S. lacrymans includes two cryptic species currently referred to as var. shastensis and var. lacrymans. Both lineages occur naturally in high altitude regions, but var. lacrymans has also spread from its natural range in Asia, and established itself in indoor environments in temperate regions worldwide. Japan was apparently colonized independently from Europe, North and South America by var. lacrymans. The population found in Australia and New Zealand seems to represent a mixture of the Japanese and the Euro-American lineages. Little genetic variation exists in the founder populations of var. lacrymans worldwide. Due to the introduction of a limited number of vic (vegetative incompatibility) alleles into the founder populations, genetically different individuals often cannot recognize self from non-self through the vegetative incompatibility response. Moreover, only a low number of MAT (mating) alleles seem to be present in Europe. Genetic analyses of the European and Japanese indoor populations have shown that S. lacrymans mainly spreads sexually via basidiospores. Surprisingly, an excess of heterozygotes has been observed in the founder populations. This could be due to heterozygote advantage caused by a limited number of MAT alleles. Recent analyses of the S. lacrymans genome provide new opportunities for further research on the dry rot fungus.